# So how often does atmospheric pressure drop below 26 anyway? **URL:** \ **Category:** Factual Questions\ **Created:** [April 10, 2012, 4:28pm UTC](https://boards.straightdope.com/t/so-how-often-does-atmospheric-pressure-drop-below-26-anyway/618377 "2012-04-10T16:28:42Z")\ **Posts on this page:** 1\ **Showing post:** 20
**Author:** ![Chessic\_Sense](https://avatars.discourse-cdn.com/v4/letter/c/7c8e57/32.png) [@Chessic\_Sense](https://boards.straightdope.com/u/Chessic_Sense)\ **Post date:** [April 11, 2012, 1:29pm UTC](https://boards.straightdope.com/t/so-how-often-does-atmospheric-pressure-drop-below-26-anyway/618377/20 "2012-04-11T13:29:13Z")
> [@Chronos](#): > > Are you assuming a fixed number of gas molecules in a sealed container of constant volume? That’s not a reasonable description of the atmosphere. Atmospheric pressure is literally the total weight of all of the air directly above a given area, so lower-density air will result in lower pressure. I asked about this in my piloting thread from last year. According to the manuals, pressure goes up on hot days. As for a sealed container, here’s one response… > [@Help the Student Pilot](https://boards.straightdope.com/t/help-the-student-pilot/556884/8): > > Another question: Weather - On a hot day, the pressure rises. This seems counter-intuitive to me, as I’d expect the air to expand in volume, not pressure. But when you’ve got gas in a container and heat it up, pressure (not volume) increases. Is the atmosphere really just one big container? > [@Help the Student Pilot](https://boards.straightdope.com/t/help-the-student-pilot/556884/10): > > The lower atmosphere essentially is, yes - air pressure is just the total weight of all the air above you. If lower layers heat up but upper ones don’t, the weight of the upper layers, resting on the lower ones, will contain them and cause their pressure to rise. So apparently, it’s a container. --- _[View the full topic](https://boards.straightdope.com/t/so-how-often-does-atmospheric-pressure-drop-below-26-anyway/618377)._